A digital library is an advancement of a conventional library. Wider role of a digital library lies in its ability to give support for service via virtual/electronic/digital network. Through its revolutionary presence, a digital library needs a testfor development. One of the tests that can be used is usqge test of interface service of magister management Digital Library (MM-Digilib) at Magister Management of Faculty of Economics, University of Indonesia. Based on theformula of Slovin and Nomogram Henry King, there are 8I valid samples out of 651 of master students accessing digital theses at Magister Management Library, Faculty of Economics, University of Indonesia. Out of indicators of usage test - efficiency, effictiveness, ease ofuse and ease ofinteraction of MM-Digilib is in general relatively good. Yet it needs to improve thefunction of Advanced Search in order to assist and shorten time in searching.